1. Field of the Invention
The invention relates to a seat belt apparatus for a vehicle, in which a seat belt can be retracted when the vehicle rolls over.
2. Description of the Related Art
Japanese Patent Laid-Open Publication No. 11-170976 discloses a seat belt apparatus for a vehicle, in which a seat belt can be retracted when the vehicle rolls over, according to related art. In the seat belt apparatus for a vehicle according to related art, a gravity sensor that detects a direction in which gravity is applied to the vehicle is provided. Based on the direction, in which gravity is applied to the vehicle, it is determined whether the vehicle will roll over. When it is determined that the vehicle will roll over, a pretensioner is operated so as to retract the seat belt, and prohibits the seat belt from being pulled out.
In the seat belt apparatus, when a determination condition as to whether the vehicle will roll over is strict, much time is required for obtaining the result of the determination, and the seat belt cannot be retracted in time when the vehicle rolls over. Accordingly, in order to retract the seat belt in time when the vehicle rolls over, it is necessary to relax the determination condition as to whether the vehicle will roll over. In this case, however, even when rollover of the vehicle is avoided due to a change in a road surface state, driving operation, or the like after it is determined that the vehicle will roll over, the seat belt is retracted, and is prohibited from being pulled out. Therefore, although the vehicle has not rolled over, an occupant is restrained.